Oxygen Enhancement Ratio in V79 Spheroids

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Abstract
Chinese hamster V79 [lung fibroblast cells] spheroids were stained with a nontoxic fluorescent stain, Hoechst 33342, which penetrates slowly into the spheroids. Single cells from these spheroids were then sorted by a fluorescence-activated cell sorter according to staining intensity (and therefore position in the spheroids). Flow cytometry characterization of the various cell subpopulations indicated that the innermost cells were more radiosensitive than expected on the basis of cell cycle position or cell thiol content. However, comparison of the radiosensitivities of ells sorted from equivalent depth from completely aerobic or anoxic V79 spheroids indicated that the oxygen enhancement ratio remained remarkably constant at 2.7 .+-. 02 through the spheroid. [This research has applications to the radiotherapy of human cancers.].